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The present study examined the longitudinal relations among work self‐efficacy beliefs, job performance and career success, defined as objective career advancements. We argued that job performance would mediate both the influence of worker's self‐efficacy beliefs on career success and the influence of career success on subsequent self‐efficacy beliefs. The participants were 976 employees of one of the largest companies in Italy, assessed at three time points (i.e., Waves 1, 2 and 3), spaced apart by 3 years. Job performance significantly mediated the relationship between self‐efficacy beliefs and subsequent career success as well as the reverse influence of career success on subsequent self‐efficacy beliefs. The posited conceptual model explained a significant portion of the variance in all endogenous variables and has implications for interventions intended to promote the development of individuals within organisations. [ABSTRACT FROM AUTHOR]

Rapid advancements in artificial intelligence (AI) are driving transformative changes in many areas, with significant environmental implications. Yet, environmental assessments for specific applications are scarce. This study presents an in‐depth life cycle assessment of "Foodforecast," a machine learning (ML) cloud service designed to reduce food waste in bakeries by optimizing sales forecasting. It covers four impact categories: global warming, abiotic resource depletion, cumulative energy demand, and freshwater eutrophication. The assessment includes both the direct environmental impacts of the ML model and the underlying system hardware, as well as the indirect benefits of avoided bakery returns compared to traditional ordering methods, using real‐world case study data. In 2022, "Foodforecast" led to an average 30% reduction in bakery returns, primarily bread and rolls, according to sales reports. The associated environmental benefits significantly outweighed the system's direct impacts by one to three orders of magnitude across impact categories and return utilization scenarios. The study identifies support activities such as service maintenance during deployment as major direct impact factors, surpassing those from cloud compute for ML operations. Data processing and inference dominate the latter, while the much‐discussed ML training plays a minor role. The environmental consequences of AI are complex and dual sided. This case study demonstrates that AI might provide environmental benefits in certain contexts, yet results are constrained by methodological challenges and data uncertainties. There remains a need for further holistic LCAs across different ML applications to inform decision‐making processes and ultimately guide the responsible use of AI. [ABSTRACT FROM AUTHOR]

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In ecological networks, cohesive groups of species may shape the evolution of interactions, serving as coevolutionary units. Ranging across network scales, from motifs to isolated components, elucidating which cohesive groups are more determinant for coevolution remains a challenge in ecology. We address this challenge by integrating 376 empirical mutualistic and antagonistic networks and coevolutionary models. We identified cohesive groups at four network scales containing a significant proportion of potential direct coevolutionary effects. Cohesive groups displayed hierarchical organisation, and potential coevolutionary effects overflowing lower‐scale groups were contained by higher‐scale groups, underscoring the hierarchy's impact. However, indirect coevolutionary effects blurred group boundaries and hierarchy, particularly under strong selection from ecological interactions. Thus, under strong selection, indirect effects render networks themselves, and not cohesive groups, as the likely coevolutionary units of ecological systems. We hypothesise hierarchical cohesive groups to also shape how other forms of direct and indirect effects propagate in ecological systems. [ABSTRACT FROM AUTHOR]

Why does a beneficial treatment effect on a longitudinal biomarker not translate into overall treatment benefit on survival, when the biomarker is in fact a prognostic factor of survival? In a recent exploratory data analysis in oncology, we were faced with this seemingly paradoxical result. To address this problem, we applied a theoretically principled methodology called dynamic path analysis, which allows us to perform mediation analysis with a longitudinal mediator and survival outcome. The aim of the analysis is to decompose the total treatment effect into a direct treatment effect and an indirect treatment effect mediated through a carefully constructed mediation path. The dynamic nature of the underlying methodology enables us to describe how these effects evolve over time, which can add to the mechanistic understanding of the underlying processes. In this paper, we present a detailed description of the dynamic path analysis framework and illustrate its application to survival mediation analysis using simulated and real data. The use case analysis provides clarity on the specific exploratory question of interest while the methodology generalizes to a wide range of applications in drug development where time‐to‐event is the primary clinical outcome of interest. [ABSTRACT FROM AUTHOR]

Temperature and resource availability are pivotal factors influencing phytoplankton community structures. Numerous prior studies demonstrated their significant influence on phytoplankton stoichiometry, cell size, and growth rates. The growth rate, serving as a reflection of an organism's success within its environment, is linked to stoichiometry and cell size. Consequently, alterations in abiotic conditions affecting cell size or stoichiometry also exert indirect effects on growth. However, such results have their limitations, as most studies used a limited number of factors and factor levels which gives us limited insights into how phytoplankton respond to environmental conditions, directly and indirectly. Here, we tested for the generality of patterns found in other studies, using a combined multiple‐factor gradient design and two single species with different size characteristics. We used a structural equation model (SEM) that allowed us to investigate the direct cumulative effects of temperature and resource availability (i.e., light, N and P) on phytoplankton growth, as well as their indirect effects on growth through changes in cell size and cell stoichiometry. Our results mostly support the results reported in previous research thus some effects can be identified as dominant effects. We identified rising temperature as the dominant driver for cell size reduction and increase in growth, and nutrient availability (i.e., N and P) as dominant factor for changes in cellular stoichiometry. However, indirect effects of temperature and resources (i.e., light and nutrients) on species' growth rates through cell size and cell stoichiometry differed across the two species suggesting different strategies to acclimate to its environment. [ABSTRACT FROM AUTHOR]

Climate change stressors are progressively simplifying biogenic habitats in the terrestrial and marine realms, and consequently altering the structure of associated species communities.Here, we used a volcanic CO2 seep in Papua New Guinea to test in situ if altered reef architecture due to ocean acidification reshuffles associated fish assemblages.We observed replacement of branching corals by massive corals at the seep, with simplified coral architectural complexity driving abundance declines between 60% and 86% for an assemblage of damselfishes associated with branching corals. An experimental test of habitat preference for a focal species indicated that acidification does not directly affect habitat selection behaviour, with changes in habitat structural complexity consequently appearing to be the stronger driver of assemblage reshuffling. Habitat health affected anti‐predator behaviour, with P. moluccensis becoming less bold on dead branching corals relative to live branching corals, irrespective of ocean acidification.We conclude that coral reef fish assemblages are likely to be more sensitive to changes in habitat structure induced by increasing pCO2 than any direct effects on behaviour, indicating that changes in coral architecture and live cover may act as important mediators of reef fish community structures in a future ocean. [ABSTRACT FROM AUTHOR]

Indirect interactions among species within ecological communities govern ecological and evolutionary processes as much as, or even more, than direct effects. In insect‐pollinated plant communities, indirect interactions between plants can be mediated by shared pollinators, and may influence plant fitness, population growth and community structure. As individuals are the entities actually interacting in nature, rather than species, downscaling a hierarchical level (i.e. from species to individuals) is essential to understand the underlying processes promoting these indirect interactions. We combined empirical data on plant–pollinator interactions collected in Mediterranean shrublands with a novel modelling framework to assess how the patterns of heterospecific and conspecific pollinator sharing between plant individuals are generated and their fitness implications. We found that the effects of flowering synchrony on pollinator sharing among conspecific and heterospecific plant individuals outperformed those of spatial distance. Our results revealed that plant individuals that shared more pollinators with conspecifics were also involved in a higher pollinator sharing with heterospecifics. For most plant species, the sharing of pollinator species between heterospecific plant individuals produced positive mean fitness outcomes, as long as plants did not share many pollinator interactions, which had negative effects on their fitness. At the level of plant individuals, we found that specific combinations of conspecific and heterospecific pollinator sharing lead to distinct reproductive outcomes that placed each individual along a competition–facilitation continuum. Interestingly, most plant species included a higher proportion of individuals likely experiencing competition compared to those potentially involved in facilitation processes. Our contribution provides novel insights into the factors responsible for local‐scale indirect interactions within communities and their individual‐level functional consequences. Such intricate patterns of indirect interactions have far‐reaching implications, as the transitions of plant individuals along competitive or facilitative processes mediated by shared mutualists may contribute significantly to the functioning and coexistence of ecological communities. [ABSTRACT FROM AUTHOR]

Feedbacks are the basic linkages of living systems. In organisms, they regulate the processes of growth and homeostasis, as well as their interactions with their world. Feedback, which Judson (1980) called 'one of the chief themes of scientific understanding,' is equally important in ecological systems. The ecological literature is rich in papers dealing with the role of feedback in various phenomena. However, we know of no comprehensive synthesis of feedbacks in ecology. Pichon et al. (2024) accomplish this, and for the first time show that ecological feedbacks can be categorized in terms of a small number of fundamental attributes. The paper brings the array of different types of feedbacks into a manageable order, providing not only the relevant theoretical framework but also guidance on methods for applying understanding to practical issues. [ABSTRACT FROM AUTHOR]

Pathogens are ubiquitous in ecosystems and play a key role in affecting host community structure. In grasslands, large grazing animals such as cattle and sheep have been shown to affect foliar fungal pathogens. However, theory and empirical studies have come to conflicting conclusions because grazers can directly and indirectly impact pathogens through a wide variety of mechanisms and various grazers may impact pathogens in different ways. A better understanding of the mechanisms by which grazers impact pathogens is important for a fundamental understanding of herbivore pathogen interactions and also to optimise grazing managements to reduce pathogen outbreaks.Here, we investigate multiple mechanisms by which livestock grazing impacts foliar fungal pathogens in grasslands. We integrate a large‐scale grazing experiment, with a removal experiment manipulating plant density and litter biomass, to identify direct and indirect effects of two herbivores on pathogens with different life histories (biotrophs and necrotrophs), in a temperate grassland in northeast China.We found that grazing by cattle and sheep had contrasting impacts: cattle grazing significantly reduced pathogen load, of both biotrophs and necrotrophs, whereas sheep grazing increased biotrophic pathogen load, but did not affect the necrotrophs. The grazing effects were mostly indirect and mediated by different impacts of the herbivores on plant community structure. Cattle grazing reduced pathogen load because it reduced the abundance of susceptible, fast‐growing plants, and the overall density of plants, while sheep grazing increased pathogen infection because it reduced the abundance of resistant plant species. Plant diversity also reduced pathogen infection but these effects were independent of the herbivores.Our results show that different herbivores can have contrasting impacts on pathogen infection through contrasting impacts on host community competence. This suggests the importance of considering multiple mechanisms simultaneously to evaluate the impact of herbivores on host‐pathogen interactions. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Livestock overgrazing causes environmental degradation, species invasion, biodiversity loss, and productivity decline, with profound consequences for ecological sustainability and human livelihoods. Habitat protection can mitigate such impacts, but we know little about how the long‐term recovery of plant communities from livestock overgrazing depends on the presence of encroaching shrubs. Here, we explored how shrub encroachment mediates the effects of habitat protection (i.e., livestock exclusion and creation of UNESCO protected areas) on biodiversity recovery and ecosystem functioning (i.e., biomass productivity). We leveraged a long‐term (15–25 years) experiment of livestock exclusion and complemented it with the removal of an encroaching shrub species in pasture areas and protected areas. We reveal that habitat protection has positive effects on patterns of recovery. Yet, the effects of habitat protection are mediated by shrub encroachment. Encroaching shrubs have net positive effects on plant diversity in pasture areas but inhibit biodiversity recovery in protected areas. The combination of habitat protection and the removal of encroaching shrubs best enhances the recovery of plant diversity and biomass productivity. A potential underlying mechanism is the shift in plant interactions from facilitation for recruitment and associated resistance to competition for water. Understanding species interactions is key to guiding conservation and restoration actions which can turn degraded ecosystems back into functional, species‐rich communities. [ABSTRACT FROM AUTHOR]

Agricultural intensification at field and landscape scales, including increased use of agrochemicals and loss of semi‐natural habitats, is a major driver of insect declines and other community changes. Efforts to understand and mitigate these effects have traditionally focused on ecological responses. At the same time, adaptations to pesticide use and habitat fragmentation in both insects and flowering plants show the potential for rapid evolution. Yet we lack an understanding of how such evolutionary responses may propagate within and between trophic levels with ensuing consequences for conservation of species and ecological functions in agroecosystems. Here, we review the literature on the consequences of agricultural intensification on plant and animal evolutionary responses and interactions. We present a novel conceptualization of evolutionary change induced by agricultural intensification at field and landscape scales and emphasize direct and indirect effects of rapid evolution on ecosystem services. We exemplify by focusing on economically and ecologically important interactions between plants and pollinators. We showcase available eco‐evolutionary theory and plant–pollinator modelling that can improve predictions of how agricultural intensification affects interaction networks, and highlight available genetic and trait‐focused methodological approaches. Specifically, we focus on how spatial genetic structure affects the probability of propagated responses, and how the structure of interaction networks modulates effects of evolutionary change in individual species. Thereby, we highlight how combined trait‐based eco‐evolutionary modelling, functionally explicit quantitative genetics, and genomic analyses may shed light on conditions where evolutionary responses impact important ecosystem services. [ABSTRACT FROM AUTHOR]

Understory assemblages associated with canopy‐forming species such as trees, kelps, and rockweeds should respond strongly to climate stressors due to strong canopy‐understory interactions. Climate change can directly and indirectly modify these assemblages, particularly during more stressful seasons and climate scenarios. However, fully understanding the seasonal impacts of different climate conditions on canopy‐reliant assemblages is difficult due to a continued emphasis on studying single‐species responses to a single future climate scenario during a single season. To examine these emergent effects, we used mesocosm experiments to expose seaweed assemblages associated with the canopy‐forming golden rockweed, Silvetia compressa, to elevated temperature and pCO2 conditions reflecting two projected greenhouse emission scenarios (RCP 2.6 [low] & RCP 4.5 [moderate]). Assemblages were grown in the presence and absence of Silvetia, and in two seasons. Relative to ambient conditions, predicted climate scenarios generally suppressed Silvetia biomass and photosynthetic efficiency. However, these effects varied seasonally—both future scenarios reduced Silvetia biomass in summer, but only the moderate scenario did so in winter. These reductions shifted the assemblage, with more extreme shifts occurring in summer. Contrarily, future scenarios did not shift assemblages within Silvetia Absent treatments, suggesting that climate primarily affected assemblages indirectly through changes in Silvetia. Mesocosm experiments were coupled with a field Silvetia removal experiment to simulate the effects of climate‐mediated Silvetia loss on natural assemblages. Consistent with the mesocosm experiment, Silvetia loss resulted in season‐specific assemblage shifts, with weaker effects observed in winter. Together, our study supports the hypotheses that climate‐mediated changes to canopy‐forming species can indirectly affect the associated assemblage, and that these effects vary seasonally. Such seasonality is important to consider as it may provide periods of recovery when conditions are less stressful, especially if we can reduce the severity of future climate scenarios. [ABSTRACT FROM AUTHOR]

This research investigated the relationships of the Dark Triad traits, humor styles, and schadenfreude with 169 participants who completed the Short Dark Triad, the Humor Style Questionnaire, and a measure of schadenfreude. Significant correlations imply that those with salient dark traits (psychopathy, Machiavellianism, narcissism) elicit pleasure from others' misfortune. Additionally, schadenfreude can be a product of self‐defeating and aggressive humor styles. Indirect effect analysis revealed the significance of the indirect effect of the measured aggressive humor style on the Dark Triad's direct effects on schadenfreude. These results imply that those with salient Dark Triad traits enjoy others' misery as a means to undermine them. Hence, individuals with salient Dark Triad traits tend to engage in downward social comparison. [ABSTRACT FROM AUTHOR]

This research investigated the relationships of the Dark Triad traits, humor styles, and schadenfreude with 169 participants who completed the Short Dark Triad, the Humor Style Questionnaire, and a measure of schadenfreude. Significant correlations imply that those with salient dark traits (psychopathy, Machiavellianism, narcissism) elicit pleasure from others' misfortune. Additionally, schadenfreude can be a product of self‐defeating and aggressive humor styles. Indirect effect analysis revealed the significance of the indirect effect of the measured aggressive humor style on the Dark Triad's direct effects on schadenfreude. These results imply that those with salient Dark Triad traits enjoy others' misery as a means to undermine them. Hence, individuals with salient Dark Triad traits tend to engage in downward social comparison. [ABSTRACT FROM AUTHOR]

Evolutionary rescue may allow species to survive environmental change, but how this mechanism operates in food webs is poorly understood. Here, the evolutionary rescue was investigated in a small model food web, systematically allowing the evolution of each single species in order to reveal how its adaptation affects the persistence of itself and others. The impact of evolution was highly species‐specific and not necessarily positive: only one species, the specialist predator, consistently had a positive impact on overall persistence. Most strikingly, evolution overwhelmingly affected other species: rescue of others (indirect rescue) was far more frequent than self‐rescue, and negative effects were nearly always indirect. This demonstrates that evolutionary rescue in food webs is inextricably bound up with species interactions, as the effects of evolution in one species ripple through the entire community. It is therefore critically important to consider the food web context in efforts to understand how species may survive global change. [ABSTRACT FROM AUTHOR]

Indirect interactions are widespread among prey species that share a common predator, but the underlying mechanisms driving these interactions are often unclear, and our ability to predict their outcome is limited.Changes in behavioural traits that impact predator space use could be a key proximal mechanism mediating indirect interactions, but there is little empirical evidence of the causes and consequences of such behavioural‐numerical response in multispecies systems.Here, we investigate the complex ecological relationships between seven prey species sharing a common predator. We used a path analysis approach on a comprehensive 9‐year data set simultaneously tracking predator space use, prey densities and prey mortality rate on key species of a simplified Arctic food web.We show that high availability of a clumped and spatially predictable prey (goose eggs) leads to a twofold reduction in predator (arctic fox) home range size, which increases local predator density and strongly decreases nest survival of an incidental prey (American golden plover). On the contrary, a scattered cyclic prey with potentially lower spatial predictability (lemming) had a weaker effect on fox space use and an overall positive impact on the survival of incidental prey.These contrasting effects underline the importance of studying behavioural responses of predators in multiprey systems and to explicitly integrate behavioural‐numerical responses in multispecies predator–prey models. [ABSTRACT FROM AUTHOR]

Although the keystone species concept was conceived of over 50 years ago, contemporary efforts to synthesize related literature have been limited. Our objective was to create a list of keystone animal species identified in the literature and to examine the variation in the traits of species and the ecosystem influences they elicit. We documented 230 species considered keystones. A clustering analysis classified them into five archetypes based on combinations of their taxonomic class, body size, trophic level, and role (consumers, modifiers, or prey). Although conservation and public perception of keystones primarily focuses on large vertebrate consumers, our analysis reveals that researchers have defined a wide diversity of keystone species, with large variation in associated ecosystem processes. Future research may confront ambiguity in the definition of keystone status, as well as clarify the type, abundance, and quality of data required to assign the term. Identifying keystones with increased rigor would not only enrich the literature but also inform intervention to safeguard threatened keystones and their associated influences on ecosystems. [ABSTRACT FROM AUTHOR]

Community ecology is built on theories that represent the strength of interactions between species as pairwise links. Higher‐order interactions (HOIs) occur when a species changes the pairwise interaction between a focal pair. Recent theoretical work has highlighted the stabilizing role of HOIs for large, simulated communities, yet it remains unclear how important higher‐order effects are in real communities. Here, we used experimental communities of aquatic protists to examine the relationship between HOIs and stability (as measured by the persistence of a species in a community). We cultured a focal pair of consumers in the presence of additional competitors and a predator and collected time series data of their abundances. We then fitted competition models with and without HOIs to measure interaction strength between the focal pair across different community compositions. We used survival analysis to measure the persistence of individual species. We found evidence that additional species positively affected persistence of the focal species and that HOIs were present in most of our communities. However, persistence was only linked to HOIs for one of the focal species. Our results vindicate community ecology theory positing that species interactions may deviate from assumptions of pairwise interactions, opening avenues to consider possible consequences for coexistence and stability. [ABSTRACT FROM AUTHOR]

It is uncontroversial to claim that the extent to which health care interventions benefit patients is a relevant consideration for health care priority setting. However, when effects accrue to the individual patient, effects of a more indirect kind may accrue to other individuals as well, such as the patient's children, friends, or partner. If, and if so how, such relational effects should be considered relevant in priority setting is contentious. In this paper, we illustrate this question by using disease‐modifying drugs for Alzheimer's disease as a case in point. The ethical analysis begins by sketching the so‐called prima facie case for ascribing moral weight to relational effects and then moves on to consider a number of objections to it. We argue that, whereas one set of objections may be dismissed, there is another set of arguments that poses more serious challenges for including relational effects in priority setting. [ABSTRACT FROM AUTHOR]

Although stable isotope analysis (SIA) is widely used to address ecological research questions, its application in an ecotoxicological context has been limited. Recent studies have proposed an effect of chemical stressors on an organism's isotope signature, questioning the use of SIA in food webs impacted by toxicants. Against this background, the present study investigates 1) whether trophic enrichment factors (TEFs; i.e., the offset in stable isotope signatures of a consumer to its diet) are altered by the neonicotinoid thiacloprid, and 2) whether tracking toxicant effects on an organism's diet composition (i.e., indirect effect) with SIA fits direct observations of consumption. To address the former, the amphipod Gammarus fossarum (Koch) was exposed to three levels (0, 0.75, and 5 µg L–1) of thiacloprid and fed with either black alder leaves or Baetis rhodani (Pictet) larvae over 6 weeks (n = 35). The thiacloprid‐induced changes in TEFs that we found were statistically significant but small compared with other factors (e.g., resource quality, consumer, and physiological condition) and thus likely of minor importance. To address the latter issue, gammarids were exposed to two levels of thiacloprid (0 and 0.75 µg L–1) and fed with either black alder leaves, live B. rhodani larvae, or both over 2 weeks (n = 10). Dietary proportions as suggested by SIA were indeed in agreement with those derived from direct observation of consumption. The present study consequently suggests that SIA is as a robust tool to detect indirect toxicant effects especially if TEFs are assessed in parallel. Environ Toxicol Chem 2023;42:1937–1945. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. [ABSTRACT FROM AUTHOR]

Anthropogenic increases in nitrogen (N) concentrations in the environment are affecting plant diversity and ecosystems worldwide, but relatively little is known about N impacts on terrestrial invertebrate communities. Here, we performed an exploratory meta‐analysis of 4365 observations from 126 publications reporting on the richness (number of taxa) or abundance (number of individuals per taxon) of terrestrial arthropods or nematodes in relation to N addition. We found that the response of invertebrates to N enrichment is highly dependent on both species' traits and local climate. The abundance of arthropods with incomplete metamorphosis, including agricultural pest species, increased in response to N enrichment. In contrast, arthropods exhibiting complete or no metamorphosis, including pollinators and detritivores, showed a declining abundance trend with increasing N enrichment, particularly in warmer climates. These contrasting and context‐dependent responses may explain why we detected no overall response of arthropod richness. For nematodes, the abundance response to N enrichment was dependent on mean annual precipitation and varied between feeding guilds. We found a declining trend in abundance with N enrichment in dry areas and an increasing trend in wet areas, with slopes differing between feeding guilds. For example, at mean levels of precipitation, bacterivore abundance showed a positive trend in response to N addition while fungivore abundance declined. We further observed an overall decline in nematode richness with N addition. These N‐induced changes in invertebrate communities could have negative consequences for various ecosystem functions and services, including those contributing to human food production. [ABSTRACT FROM AUTHOR]

Summary: Parasites can catalyze or inhibit interactions between their hosts and other species, but the ecosystem‐level effects of such interaction modifications are poorly understood.We conducted a large‐scale field experiment in temperate grasslands of China to understand how foliar fungal pathogens influenced top‐down effects of cattle on plant diversity and productivity.When foliar pathogens were suppressed, cattle grazing strongly reduced biomass of the dominant grass, Leymus chinensis, generating competitive release that significantly increased community‐level species richness and evenness. In the absence of grazing, pathogen attack on L. chinensis had no measurable effect on host biomass. However, pathogens disrupted top‐down effects of herbivory by inhibiting grazing effects on plant biomass and species richness. Mechanistically, fungal pathogens were linked to increased alkaloid and reduced nitrogen levels in leaf tissue, which appeared to deter cattle grazing on L. chinensis.In conclusion, foliar pathogens can suppress top‐down effects of large herbivores on grassland community composition and ecosystem function by modifying the strength of their host's interactions with dominant consumers. Parasites may act as modulators of ecosystem function when their direct effects on host abundance are overshadowed by powerful influences on host traits that modify their interactions with competitors, herbivores, or predators. [ABSTRACT FROM AUTHOR]

Copepods play a critical role in the carbon cycle of the planet – they mediate the sequestration of carbon into the deep ocean and are the trophic link between phytoplankton and marine food webs. Global change stressors that decrease copepod productivity create the potential for catastrophic positive feedback loops. Accordingly, a growing list of studies examine the evolutionary capacity of copepods to adapt to the two primary stressors associated with global change: warmer temperatures and lower pH. But the evolutionary capacity of copepods to adapt to changing food regimes, the third major stressor associated with global change, remains unknown. We used experimental evolution to explore how a 10‐fold difference in food availability affects life history evolution in the copepod, Tisbe sp. over 2 years, and spanning 30+ generations. Different food regimes evoked evolutionary responses across the entire copepod life history: we observed evolution in body size, size‐fecundity relationships and offspring investment strategies. Our results suggest that changes to food regimes reshape life histories and that cryptic evolution in traits such as body size is likely. We demonstrate that evolution in response to changes in ocean productivity will alter consumer life histories and may distort trophic links in marine foodchains. Evolution in response to changing phytoplankton productivity may alter the efficacy of the global carbon pump in ways that have not been anticipated until now. [ABSTRACT FROM AUTHOR]

Mast seeding causes strong fluctuations in populations of forest animals. Thus, this phenomenon can be used as a natural experiment to examine how variation in host abundance affects parasite loads. We investigated fleas infesting yellow‐necked mice in beech forest after 2 mast and 2 non‐mast years. We tested 2 mutually exclusive scenarios: (1) as predicted by classical models of density‐dependent transmission, an increase in host density will cause an increase in ectoparasite abundance (defined as the number of parasites per host), versus (2) an increase in host density will cause a decline in flea abundance ("dilution," which is thought to occur when parasite population growth is slower than that of the host). In addition, we assessed whether masting alters the relationship between host traits (sex and body mass) and flea abundance. We found a hump‐shaped relationship between host and flea abundance. Thus, the most basic predictions are too simple to describe ectoparasite dynamics in this system. In addition, masting modified seasonal dynamics of flea abundance, but did not affect the relationship between host traits and flea abundance (individuals with the highest body mass hosted the most fleas; after controlling for body mass, parasite abundance did not vary between sexes). Our results demonstrate that pulses of tree reproduction can indirectly, through changes in host densities, drive patterns of ectoparasite infestation. [ABSTRACT FROM AUTHOR]

Consumptive effects (CEs) of predation have been well‐studied in most aquatic systems, but nonconsumptive effects (NCEs) on prey have only recently received limited attention. As aquatic consumers, tadpoles have traditionally been considered strict herbivores, leaving their predatory impacts via CEs and NCEs largely unexplored. We quantified omnivory among wood frog (Lithobates sylvaticus) tadpoles and characterized their CEs and NCEs on invertebrate communities. Tadpoles from natural ponds were dissected to quantify the frequency of omnivory generally, as well as specifically in relation to pond size and tadpole morphology. Additional tadpoles were employed in a mesocosm experiment that manipulated tadpole presence (absent, caged, or free‐swimming) to quantify CEs and NCEs on freshwater zooplankton and macroinvertebrate communities. Over 70% of tadpoles in natural ponds engaged in omnivory, primarily on zooplankton, and tadpoles with wider heads and deeper tails were more likely to be omnivorous. Tadpoles in mesocosms exhibited CEs and NCEs on invertebrate communities, with stronger effects exerted on zooplankton than macroinvertebrates. The NCEs of tadpoles on invertebrates likely included production of predatory chemical cues that influenced invertebrate behavior, abundance, and community composition. Because tadpoles are often the dominant vertebrate predators in ephemeral aquatic ecosystems, this study stresses their ecological importance in structuring aquatic communities. [ABSTRACT FROM AUTHOR]

Summary: Changes in resources (e.g. nitrogen) and enemies (e.g. foliar pathogens) are key drivers of plant diversity and composition. However, their effects have not been connected to the niche and fitness differences that determine multispecies coexistence.Here, we combined a structuralist theoretical approach with a detailed grassland experiment factorially applying nitrogen addition and foliar fungal pathogen suppression to evaluate the joint effect of nitrogen and pathogens on niche and fitness differences, across a gradient from two to six interacting species.Nitrogen addition and pathogen suppression modified species interaction strengths and intrinsic growth rates, leading to reduced multispecies fitness differences. However, contrary to expected, we also observed that they promote stabilising niche differences. Although these modifications did not substantially alter species richness, they predicted major changes in community composition. Indirect interactions between species explained these community changes in smaller assemblages (three and four species) but lost importance in favour of direct pairwise interactions when more species were involved (five and six).Altogether, our work shows that explicitly considering the number of interacting species is critical for better understanding the direct and indirect processes by which nitrogen enrichment and pathogen communities shape coexistence in grasslands. [ABSTRACT FROM AUTHOR]

Burrowing animals can profoundly affect the biological structure and ecosystem functions of their environments. For instance, burrowing crabs increase sediment deposition and facilitate sediment homogenization and turnover, with potential impacts to sediment biogeochemistry. However, the relative importance of burrowing crabs on sediment dynamics can vary considerably between, and within, habitats. Sediment properties influence how burrowing crabs will affect edaphic conditions, but these studies often assume homogenous sediment conditions and fail to consider how sediment properties change with depth. Thus, understanding how burrowing crab effects on sediment properties are influenced by the vertical sediment profile should inform where burrowing crabs structure edaphic conditions. Here, we conducted an intensive field survey across three tidal salt marshes with variable sediment properties to understand if marsh vertical sediment profiles can help predict the nature of burrowing crab–sediment relationships. We found that burrowing crabs homogenize sediments in all marshes, but their effects on sediment homogenization and edaphic conditions were greater in marshes with highly stratified vertical sediment profiles. Our study suggests that understanding the vertical sediment profile of a salt marsh may provide critical insights into how crab burrowing may influence the edaphic conditions and physical characteristics of marsh surface sediments—especially in restored, created, and managed salt marshes. [ABSTRACT FROM AUTHOR]

Forest soils harbour a vast array of organisms that govern the processing of organic matter. Through their trophic interactions, they give rise to carbon flows that sustain soil ecosystem functioning. Understanding how soil food webs shape carbon flows may enhance our knowledge about the role of biodiversity on soil processes.In this work, we assembled trophic networks representing soil food webs of two beech forests during spring and autumn, and compiled mass‐balanced models quantifying carbon flows between their components. These models were investigated using network analysis to identify the role of the components on carbon flow, cycling and functional trophic relationships. Moreover, we explored how the structure of carbon exchanges promote efficiency and stability.Results indicate the importance of indirect interactions. Most trophic groups exhibit a diffuse dependency on all the compartments for their carbon requirement although certain groups such as Collembola play the role of hubs in distributing carbon. Indirect interactions often reverse the impacts of direct trophic relationships being antagonistic to the direction of change predicted based on predator–prey interactions. The high incidence of generalist feeding habits increases the redundancy of energy channels thereby making such food webs more resilient against perturbations but at the expense of carbon transfer efficiency.Although differences can be observed across sites and periods, food web structure rather than environmental variability seems to be the main factor responsible for patterns of carbon flows in the two beech forests. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

The outcomes of species interactions can vary greatly in time and space with the outcomes of some interactions determined by priority effects. On coral reefs, benthic algae rapidly colonize disturbed substrate. In the absence of top‐down control from herbivorous fishes, these algae can inhibit the recruitment of reef‐building corals, leading to a persistent phase shift to a macroalgae‐dominated state. Yet, corals may also inhibit colonization by macroalgae, and therefore the effects of herbivores on algal communities may be strongest following disturbances that reduce coral cover. Here, we report the results from experiments conducted on the fore reef of Moorea, French Polynesia, where we: (1) tested the ability of macroalgae to invade coral‐dominated and coral‐depauperate communities under different levels of herbivory, (2) explored the ability of juvenile corals (Pocillopora spp.) to suppress macroalgae, and (3) quantified the direct and indirect effects of fish herbivores and corallivores on juvenile corals. We found that macroalgae proliferated when herbivory was low but only in recently disturbed communities where coral cover was also low. When coral cover was <10%, macroalgae increased 20‐fold within 1 year under reduced herbivory conditions relative to high herbivory controls. Yet, when coral cover was high (50%), macroalgae were suppressed irrespective of the level of herbivory despite ample space for algal colonization. Once established in communities with low herbivory and low coral cover, macroalgae suppressed recruitment of coral larvae, reducing the capacity for coral replenishment. However, when we experimentally established small juvenile corals (2 cm diameter) following a disturbance, juvenile corals inhibited macroalgae from invading local neighborhoods, even in the absence of herbivores, indicating a strong priority effect in macroalgae–coral interactions. Surprisingly, fishes that initially facilitated coral recruitment by controlling algae had a net negative effect on juvenile corals via predation. Corallivores reduced the growth rates of corals exposed to fishes by ~30% relative to fish exclosures, despite increased competition with macroalgae within the exclosures. These results highlight that different processes are important for structuring coral reef ecosystems at different successional stages and underscore the need to consider multiple ecological processes and historical contingencies to predict coral community dynamics. [ABSTRACT FROM AUTHOR]

Apparent competition is one mechanism that can contribute to the complex dynamics observed in natural systems, yet it remains understudied in empirical systems. Understanding the dynamics that shape the outcome of processes like apparent competition is vital for appreciating how they influence natural systems.We empirically evaluated the role of indirect trophic interactions in driving apparent competition in a model laboratory system. Our experimental system was designed to let us evaluate combined direct and indirect interactions among species.Here we describe the results of a factorial experiment using two noncompeting prey (Colpidium kleini, a heterotroph, and Chlamydomonas reinhardtii, an autotroph) consumed by a generalist predator Euplotes eurystomus to explore the dynamics of apparent competition. To gain intuition into the potential mechanism driving the asymmetry in the observed results, we further explored the system using structural equation modelling.Our results show an important role of positive interactions and indirect effects contributing to apparent competition in this system with a marked asymmetrical outcome favouring one prey, Chlamydomonas. The selected structural equation supports a role of indirect facilitation; although Chlamydomonas (a photoautotroph) and Colpidium (a bacterivore) use different resources and therefor do not directly compete, Colpidium reduces bacteria that may compete with Chlamydomonas. In addition, formation of colonies by Chlamydomonas in response to predation by Euplotes provides an antipredator defence not available to Colpidium.Asymmetric apparent competition may be more common in natural systems than the symmetric interaction originally proposed in classic theory, suggesting that exploration of the mechanisms driving the asymmetry of the interaction can be a fruitful area of further research to better our understanding of interspecific interactions and community dynamics. [ABSTRACT FROM AUTHOR]

Prey handling processes are considered a dominant mechanism leading to short‐term positive indirect effects between prey that share a predator. However, a growing body of research indicates that predators are not necessarily limited by such processes in the wild. Density‐dependent changes in predator foraging behavior can also generate positive indirect effects but they are rarely included as explicit functions of prey densities in functional response models. With the aim of untangling proximate mechanisms of species interactions in natural communities and improving our ability to quantify interaction strength, we extended the multi‐prey version of the Holling disk equation by including density‐dependent changes in predator foraging behavior. Our model, based on species traits and behavior, was inspired by the vertebrate community of the arctic tundra, where the main predator (the arctic fox) is an active forager feeding primarily on cyclic small rodent (lemming) and eggs of various tundra‐nesting bird species. Short‐term positive indirect effects of lemmings on birds have been documented over the circumpolar Arctic but the underlying mechanisms remain poorly understood. We used a unique data set, containing high‐frequency GPS tracking, accelerometer, behavioral, and experimental data to parameterize the multi‐prey model, and a 15‐year time series of prey densities and bird nesting success to evaluate interaction strength between species. We found that (1) prey handling processes play a minor role in our system and (2) changes in arctic fox daily activity budget and distance traveled can partly explain the predation release on birds observed during lemming peaks. These adjustments in predator foraging behavior with respect to the main prey density thus appear as the dominant mechanism leading to positive indirect effects commonly reported among arctic tundra prey. Density‐dependent changes in functional response components have been little studied in natural vertebrate communities and deserve more attention to improve our ability to quantify the strength of species interactions. [ABSTRACT FROM AUTHOR]

Conservation of endangered social wildlife in disturbance‐prone forests is challenging because direct and indirect effects of management strategies developed at the time of species' listing when population density is low may change under high‐density conditions in locally recovered populations. Here, we used piecewise structural equation modeling to evaluate direct and indirect drivers of productivity in the federally endangered cooperatively breeding red‐cockaded woodpecker Dryobates borealis (RCW) on Savannah River Site, South Carolina, USA. We estimated direct and indirect relationships among group size, neighboring group sizes, fledgling production, density of cavity tree clusters occupied by RCWs, area satisfying threshold criteria of ≥22 stems ha−1 of pines ≥35.6 cm diameter at breast height (dbh), <1.4 m2 ha−1 basal area (BA) of hardwoods 7.6–22.9 cm dbh, and <6% hardwood canopy cover, and area treated with prescribed fire, and tested whether group size mediated indirect effects of area satisfying threshold criteria on fledgling production. Increases in area with ≥22 stems ha−1 of pines ≥35.6 cm dbh and <1.4 m2 ha−1 BA of hardwoods 7.6–22.9 cm dbh, and area treated with prescribed fire, but not area with <6% hardwood canopy cover, had direct positive effects on group size. Group size and area treated with prescribed fire, but not area satisfying threshold criteria, had direct positive effects on fledgling production. The direct effect of neighboring group sizes on fledgling production was negative and smaller relative to the direct positive effect of group size on fledgling production. Overall, our results indicate positive direct effects of group size on fledgling production outweighed negative direct effects of neighboring group sizes, and that group size mediated positive indirect effects of area satisfying structural threshold criteria on fledgling production. These findings indicate that ongoing forest management aimed to increase area with ≥22 pines ha−1 ≥35.6 cm dbh and <1.4 m2 ha−1 BA of hardwoods 7.6–22.9 cm dbh will promote large group sizes, which in turn improve fledgling production and offset costs of heightened competition with neighboring groups under high‐density conditions. Additionally, positive effects of area treated with prescribed fire on RCW group size and fledgling production indicate prescribed fire has unique contributions to woodpecker productivity, likely via direct effects on forest structure and potentially indirect effects on arthropod prey available to foraging RCWs. By simultaneously accounting for multiple drivers of productivity in social wildlife, our study contributes to the understanding of how increases in social wildlife population sizes can alter previously documented habitat‐fitness relationships. [ABSTRACT FROM AUTHOR]

Insecticides used to combat outbreaks of forest defoliators can adversely affect non‐target arthropods. Forestry insecticides typically suppress Lepidoptera larvae which are the cornerstone of the canopy community of deciduous oak forests. The abrupt removal of this dominant component of the food web could have far‐reaching implications for forest ecosystems, yet it is rarely investigated in practice owing to several methodological shortcomings. The taxonomic impediment and the biased nature of arthropod sampling techniques particularly impede the assessment of insecticide impacts on diverse communities.To tackle this issue, we propose an experimental approach combining sampling by pyrethrum knockdown and species determination via DNA metabarcoding, using community subsampling to derive estimates of species abundances. We applied this protocol to investigate the short‐term effects of the insecticides diflubenzuron (DFB) and Bacillus thuringiensis var. kurstaki (BTK) on canopy‐dwelling arthropod communities in German oak woodlands.Our approach allowed us to detect most of the diversity and integrate species abundances in our analyses. By classifying arthropod species into assemblages based on their expected sensitivity rather than coarse taxonomic groupings, we could unveil substantial effects of DFB across multiple taxa 5 weeks after application.Although strong effects on single species appear related to direct toxicity, substantial impacts of DFB on parasitoids and xylophagous beetles suggest that anti‐defoliator treatments can have previously unsuspected indirect effects on some components of forest arthropod communities. The impacts of BTK on community structure were consistent with that of DFB though much weaker.Synthesis and applications. Comparing diversity patterns in the arthropod communities of sprayed and unsprayed oak canopies, our results show that selective insecticides can alter species diversity in presumably non‐sensitive taxa. Even though the ecological significance of these impacts has yet to be assessed in an operational setting, their existence calls for increased regulatory scrutiny on indirect effects. As community approaches become more attainable with the rapid development of DNA metabarcoding, we suggest the inclusion of community‐level end points as regulatory requirements for the approval of forest‐use insecticides. [ABSTRACT FROM AUTHOR]

Species reintroductions can be used as a conservation strategy to restore ecological interactions and the functionality of impoverished ecosystems. The ecological effects of reintroductions go beyond restoring pairwise interactions, because reintroductions can change how extant species are indirectly linked to each other in an ecological community. These indirect pathways, in turn, may shape a myriad of ecological and evolutionary processes operating in ecological systems. Here, we investigated how reintroductions may affect the direct and indirect pathways connecting species in ecological networks. We modeled the potential effects of the reintroduction of four frugivore species (channel‐billed toucans, red‐humped agoutis, brown howler monkeys and yellow‐footed tortoises) to the local seed dispersal network in an Atlantic Forest site, the Tijuca National Park (Rio de Janeiro, Brazil). We used a seed dispersal interaction dataset together with data on species occurrences in Tijuca to build network models. Then, we calculated how network structure and the total amount of indirect effects varied across simulated networks with and without the reintroduced species. Using random reintroduction simulations, we tested if the observed network changes were expected merely from the increase in species richness. The reintroduction of the frugivore species increased network connectance, nestedness, robustness, number of pathways and total amount of indirect effects in all simulated networks. The increase in number of pathways with the addition of the four reintroduced species was greater than the sum of isolated effects for each species, because some interaction pathways contained several reintroduced species. These changes in network metrics were significantly greater than if a randomly chosen set of four species was reintroduced. Furthermore, our results indicate that multiple reintroductions in the same area, known as refaunation, may have an even greater restoration effect than single species reintroductions through increased indirect connections in the network. [ABSTRACT FROM AUTHOR]

Anthropogenic climate change poses a substantial challenge to many organisms, to which they need to respond to avoid fitness reductions. Investigating responses to environmental change is particularly interesting in herbivores, as they are potentially affected by indirect effects mediated via variation in host‐plant quality. We here use the herbivorous insect Pieris napi to investigate geographic variation in the response to variation in food quality. We performed a common garden experiment using replicated populations from Germany and Italy, and manipulated host quality by growing host plants at different temperature and water regimes. We found that feeding on plants grown at a higher temperature generally diminished the performance of P. napi, evidenced by a prolonged development time and reduced larval growth rate, body mass, fat content, and phenoloxidase activity. Genotype by environment interactions (G × E) were present in several performance traits, indicating that Italian populations (1) respond more strongly to variation in host‐plant quality and (2) are more sensitive to poor food quality than German ones. This may reflect a cost of the rapid lifestyle found in Italian populations. Consequently, German populations may be more resilient against environmental perturbations and may perhaps even benefit from warmer temperatures, while Italian populations will likely suffer from the concomitantly reduced host‐plant quality. Our study thus exemplifies how investigating G × E may help to better understand the vulnerability of populations to climate change. [ABSTRACT FROM AUTHOR]

The characteristics of participatory institutions can be articulated in three main dimensions: input, process and output. The common assumption is that a dependency relationship exists, with process serving as a mediator between input and output. This paper puts the model to a rare empirical test drawing on a unique dataset of 70 Spanish advisory councils. Through a combination of exploratory factor and path analyses, we analyse the dimensionality of input, process and output and investigate the direct and indirect impact of inputs on process and outputs. Our analysis provides evidence that input factors have a direct impact on the output factor transparency, but their impact on effects on policy and participant satisfaction is mediated by the process factor deliberation. Further, the capacity of the public administration to steer the advisory council (wardship) mediates negatively the impact of input variables on transparency. The analysis provides a nuanced account of how different input and process design characteristics of participatory institutions have profound direct and indirect effects on their outputs. [ABSTRACT FROM AUTHOR]

Evaluating the effects of multiple stressors on ecosystems is becoming increasingly vital with global changes. The role of species interactions in propagating the effects of stressors, although widely acknowledged, has yet to be formally explored. Here, we conceptualise how stressors propagate through food webs and explore how they affect simulated three‐species motifs and food webs of the Canadian St. Lawrence System. We find that overlooking species interactions invariably underestimate the effects of stressors, and that synergistic and antagonistic effects through food webs are prevalent. We also find that interaction type influences a species' susceptibility to stressors; species in omnivory and tri‐trophic food chain interactions in particular are sensitive and prone to synergistic and antagonistic effects. Finally, we find that apex predators were negatively affected and mesopredators benefited from the effects of stressors due to their trophic position in the St. Lawrence System, but that species sensitivity is dependent on food web structure. In conceptualising the effects of multiple stressors on food webs, we bring theory closer to practice and show that considering the intricacies of ecological communities is key to assess the net effects of stressors on species. [ABSTRACT FROM AUTHOR]

Selection on flowering time in plants is often mediated by multiple agents, including climatic conditions and the intensity of mutualistic and antagonistic interactions with animals. These selective agents can have both direct and indirect effects. For example, climate might not only influence phenotypic selection on flowering time directly by affecting plant physiology, but it can also alter selection indirectly by modifying the seasonal activity and relative timing of animals interacting with plants. We used 21 yr of data to identify the drivers of selection on flowering time in the perennial herb Lathyrus vernus, and to examine if antagonistic plant–animal interactions mediate effects of climate on selection. We examined the fitness consequences of vertebrate grazing and predispersal seed predation, and how these effects varied among years and among individuals within years. Although both antagonistic plant–animal interactions had important negative effects on plant fitness, only grazing intensity was consistently related to plant phenology, being higher in early‐flowering individuals. Spring temperature influenced the intensity of both plant–animal interactions, as well as the covariance between seed predation and plant phenology. However, only differences in grazing intensity among years were associated with differences in selection on flowering time; the strength of selection for early flowering being stronger in years with lower mean intensity of grazing. Our results illustrate how climatic conditions can influence plant–animal interactions that are important selective agents for plant traits. A broader implication of our findings is that both ecological and evolutionary responses to climatic changes might be indirect, and largely mediated by species interactions. [ABSTRACT FROM AUTHOR]

Pollinators have been declining in recent years due to changes in land use, and the negative impacts on food production are concern. Wildflowers play an important role in maintaining pollinators and pollination services in agricultural landscapes, but little is known about the effects of wildflowers at field margins on crop pollinators. We aimed to clarify the relationship between crop pollination and the species richness of wildflowers at field margins through sharing of flower visitors. We focused on insects that visit the flowers of buckwheat, Fagopyrum esculentum, in fields in Japan. Field surveys were conducted to investigate flower‐visiting insect communities in both the pre‐blooming and blooming periods of buckwheat in summer and autumn. The community structure of flower‐visiting insects differed between buckwheat and wildflowers in both seasons, but buckwheat shared beetles with co‐flowering plants in autumn. The abundance of insects visiting buckwheat increased with species richness of co‐flowering plants in autumn but was not related to wildflowers in summer. The morphological similarity of floral traits would not be important for these positive effects of wildflowers. Thus, co‐flowering plants have positive or neutral effects on the insects visiting buckwheat, which may contribute to the enhancement of buckwheat yields. [ABSTRACT FROM AUTHOR]

Small cumulus clouds over the western United States were measured via airborne instruments during the wildfire season in summer of 2018. Statistics of the sampled clouds are presented and compared to smoke aerosol properties. Cloud droplet concentrations were enhanced in regions impacted by biomass burning smoke, at times exceeding 3,000 cm−3. Images and elemental composition of individual smoke particles and cloud droplet residuals are presented and show that most are dominantly organic, internally mixed with some inorganic elements. Despite their high organic content and relatively low hygroscopicity, on average about half of smoke aerosol particles >80 nm diameter formed cloud droplets. This reduced cloud droplet size in small, smoke‐impacted clouds. A number of complex and competing climatic impacts may result from wide‐spread reductions in cloud droplet size due to wildfires prevalent across the region during summer months. Plain Language Summary: Wildfires over the western United States produce large quantities of smoke during the summer months. The smoke includes airborne particles that can act as nuclei for forming individual droplets in clouds. Particles and clouds in the region were sampled with a research aircraft to measure the properties of smoke particles and how they influenced the properties of small cumulus clouds. Clouds were strongly influenced by smoke across the western U.S. On average, sampled clouds had about 5x as many droplets, and droplets were about 1/2 the size, as in clouds not influenced by smoke. Because of their small droplet sizes, these smoky clouds are expected to reflect more light and produce less rain than clouds in clean air. Other complex effects are possible due to warming impacts of the smoke itself, and due to other potential impacts of smoke aerosols on larger, deeper clouds. Key Points: Western wildfires produce organic particles that readily act as cloud condensation nuclei due to their large size and partial hygroscopicityWildfire smoke strongly impacts the microphysics of small cumulus clouds, which have high droplet concentrations and small droplet sizesDiverse impacts on radiative forcing and precipitation are possible over the western U.S. and downwind due to wildfire smoke [ABSTRACT FROM AUTHOR]

1. The decline in insect abundance and diversity observed in many ecosystems is of major concern because of the long‐term consequences for ecosystem function and stability. 2. Species in ecological communities are connected through interactions forming complex networks. Therefore, initial extinctions can cause further species losses through co‐extinctions and extinction cascades, where single extinctions can lead to waves of secondary extinctions. Such knock‐on effects can multiply the initial impact of disturbances, thereby largely adding to the erosion of biodiversity. However, our knowledge of their importance for the current insect decline is hampered because secondary extinctions are challenging to both detect and predict. 3. In this review, we bring together theory and knowledge about secondary extinctions in the light of the main drivers of insect decline. We evaluate potential and evidence for cascading extinction for the different drivers and identify major pathways. By providing selected examples we discuss how habitat loss, pollution, species invasions, climate change and overexploitation can cause cascading extinctions. We argue that habitat loss and pollution in particular have the largest potential for such extinctions by changing community structure, the physical environment, and community robustness. 4. Overall, cascading extinction are part of an ecosystems' response to anthropogenic drivers but are so far not explicitly measured in their contribution when evaluating biodiversity loss. This knowledge is necessary to predict biodiversity loss and find strategies to buffer against the devastating long‐term impact of habitat loss, pollution, species invasions, and climate change. [ABSTRACT FROM AUTHOR]

Arthropod communities dwelling in adjacent habitats are able to impact one another via shared natural enemies. In agricultural landscapes, drastic differences in resource availability between crop and non‐crop habitats cause variation in insect herbivore densities over short distances, potentially driving inter‐habitat effects. Moreover, the composition of the landscape in which the habitats are embedded likely affects realised attack rates from natural enemies via impacts on local arthropod community structure.Here, we examine indirect effects between herbivore species within and between habitat types by calculating the potential for apparent competition between multiple populations. Firstly, we aim to determine how disparities in resource availability impact the strength of the potential for apparent competition occurring between habitats, secondly to examine the impact of landscape composition upon these effects, and finally to couch these observations in reality by investigating the link between the potential for apparent competition and realised attack rates.We used DNA metabarcoding to characterise host–parasitoid interactions within two habitat types (with divergent nutrient inputs) at 11 locations with variable landscape composition within an agroecosystem context. We then used these interaction networks to estimate the potential for apparent competition between each host pair and to compare expected versus realised attack rates across the system.Shared natural enemies were found to structure host herbivore communities within and across habitat boundaries. The size of this effect was related to the resource availability of habitats, such that the habitat with high nutrient input exerted a stronger effect. The overall potential for apparent competition declined with increasing land‐use intensity in the surrounding landscape and exhibited a discernible impact on realised attack rates upon herbivore species.Thus, our results suggest that increasing the proportion of perennial habitat in agroecosystems could increase the prevalence of indirect effects such as apparent competition among insect herbivore communities, potentially leading to enhanced population regulation via increased attack rates from natural enemies like parasitoid wasps. [ABSTRACT FROM AUTHOR]

Anthropogenically influenced habitats are becoming increasingly impacted by multiple invasive species that can regionally control main ecological processes and functions. Management requires predictions of invasive species' effects, but multiple invasions may cause unpredictable outcomes, for example, synergistic impacts or interactions among trophic levels causing trophic cascades. The Baltic Sea is prone to species invasions that increasingly occur at multiple trophic levels. We used a laboratory experiment to test whether multiple invasive predators may cause interactive effects in the Baltic Sea. In aquaria, we simulated a coastal community that has developed dominated by invasive species—the decapod predators Palaemon elegans and Rhithropanopeus harrisii, the amphipod grazer Gammarus tigrinus, and the filter‐feeder Dreissena polymorpha. The orthogonal experiment determined separate and interactive effects from predators on the lower trophic level invasive species and native algae including the foundation species Fucus radicans. The main result was that while both predators significantly impacted the community, in no cases were their effects interactive. Another important result was that P. elegans appeared to cause a trophic cascade, as in its presence F. radicans and its epiphytes had the greatest biomass while G. tigrinus grazers were heavily reduced. G. tigrinus were negatively correlated with F. radicans biomass, so variable amphipod grazing may be the link allowing an indirect effect of P. elegans on F. radicans. R. harrisii also reduced G. tigrinus abundance but did not affect F. radicans biomass. Both predators significantly affected the lengths of F. radicans plant stems that were comprised of new vegetative growth—P. elegans reduced the lengths of new vegetative tissue while R. harrisii increased it. Thus, the presence of P. elegans induced shorter and denser F. radicans bushes compared to taller and thinner bushes observed in other treatments. Lastly, R. harrisii caused significant declines in D. polymorpha numbers. Overall, ecological management needs to consider positive effects from predator invasion which may reduce grazing pressure on low trophic level foundation species. A trophic cascade involving two invasive species highlights the importance of multi‐species approaches to management of Baltic Sea invasive species and in other regions prone to biological invasions. [ABSTRACT FROM AUTHOR]

The interplay between top‐down and bottom‐up processes determines ecosystem productivity. Yet, the factors that mediate the balance between these opposing forces remain poorly understood. Furthering this challenge, complex and often cryptic factors like ecosystem engineering and trait‐mediated interactions may play major roles in mediating the outcomes of top‐down and bottom‐up interactions. In semiarid grasslands of northeastern China, we conducted a large‐scale, three‐year experiment to evaluate how soil engineering by ants and plasticity in plants independently and jointly influenced the top‐down effects of grazing by a ubiquitous herbivore (cattle) on aboveground standing biomass of the dominant perennial grass, Leymus chinensis. Herbivory had strong top‐down effects, reducing L. chinensis AB by 25% relative to baseline levels without cattle or ants. In contrast, soil engineering by ants facilitated weak bottom‐up effects in the absence of herbivory. However, in the presence of herbivory, soil engineering effects were strong enough to fully offset herbivore removal of aboveground biomass. This outcome was mediated by L. chinensis's plasticity in reallocating growth from below‐ to aboveground biomass, a result linked to additive effects of engineers and herbivores increasing soil N availability and engineering effects improving soil structure. Soil engineering increased soil N by 12%, promoting aboveground biomass. Herbivores increased soil N by 13% via defecation, but this increase failed to offset their reductions in aboveground biomass in isolation. However, when combined, engineers and herbivores increased soil N by 26% and engineers improved soil bulk density, facilitating L. chinensis to shift resource allocations from below‐ to aboveground biomass sufficiently to fully offset herbivore suppression of aboveground biomass. Our results demonstrate that soil engineering and trait‐mediated effects of plant plasticity can strongly mediate the outcome of top‐down and bottom‐up interactions. These cryptic but perhaps ubiquitous processes may help to explain the long‐debated phenomenon of plant compensatory responses to large grazers. [ABSTRACT FROM AUTHOR]

Infectious diseases can directly affect women and men differently. During the COVID-19 pandemic, higher case fatality rates have been observed in men in most countries. There is growing evidence, however, that while organisational changes to healthcare delivery have occurred to protect those vulnerable to the virus (staff and patients), these may lead to indirect, potentially harmful consequences, particularly to vulnerable groups including pregnant women. These encompass reduced access to antenatal and postnatal care, with a lack of in-person clinics impacting the ability to screen for physical, psychological and social issues such as elevated blood pressure, mental health issues and sex-based violence. Indirect consequences also encompass a lack of equity when considering the inclusion of pregnant women in COVID-19 research and their absence from vaccine trials, leading to a lack of safety data for breastfeeding and pregnant women. The risk-benefit analysis of these changes to healthcare delivery remains to be fully evaluated, but the battle against COVID-19 cannot come at the expense of losing existing quality standards in other areas of healthcare, especially for maternal health. [ABSTRACT FROM AUTHOR]

Aims: Desert dominant plants commonly facilitate plant communities within their canopies. Although substantial research has examined the direct consequences of this effect, a mechanistic understanding of indirect effects mediated via beneficiary plants is still relatively limited. We tested the hypothesis that the net positive outcome of dominant plants on beneficiaries extends to a series of interactions including indirect competition or facilitation. To test this hypothesis, we aggregated two years of field surveys with a manipulative experiment. Location: Atiquipa, Southern Peru. Methods: We surveyed the understorey plant community of the dominant tree Caesalpinia spinosa and compared it to that of open microsites. Field manipulations included removal of plant neighbourhoods of two target annual species in the understorey of the dominant plant Caesalpinia spinosa and adjacent open microsites. In the surveys, we measured plant density, and in the removal experiment, plant height, fruit set, and biomass of the targets. Results: In the surveys, density of Fuertisimalva peruviana, a target species, was negatively dependent on understorey neighbours’ density. Neighbourhood removal did not affect fruit set or biomass of Fuertisimalva peruviana in tree understories or open microsites. Neighbourhood removal around Plantago limensis increased biomass, plant height and fruit set, and changed the effect of the dominant tree from positive to negative for biomass. Conclusions: Understorey plant neighbours can mediate the direct effects of dominant plants in deserts, but responses to these indirect effects can be species‐specific. The facilitative effects of dominant plants represent key coexistence mechanisms because they reduce stress and generate extended series of interactions not necessarily present in the open.Desert dominant plants commonly facilitate plant communities within their canopies. We tested the hypothesis that the net positive outcome of dominant plants on beneficiaries extends to a series of interactions including indirect effects. Using field surveys and a manipulative experiment over two years we found that understorey plant neighbours can mediate indirect effects of dominant plants, although this is species‐specific. [ABSTRACT FROM AUTHOR]

Functional responses relate a consumer's feeding rates to variation in its abiotic and biotic environment, providing insight into consumer behaviour and fitness, and underpinning population and food‐web dynamics. Despite their broad relevance and long‐standing history, we show here that the types of density dependence found in classic resource‐ and consumer‐dependent functional‐response models equate to strong and often untenable assumptions about the independence of processes underlying feeding rates. We first demonstrate mathematically how to quantify non‐independence between feeding and consumer interference and between feeding on multiple resources. We then analyse two large collections of functional‐response data sets to show that non‐independence is pervasive and borne out in previously hidden forms of density dependence. Our results provide a new lens through which to view variation in consumer feeding rates and disentangle the biological underpinnings of species interactions in multi‐species contexts. [ABSTRACT FROM AUTHOR]

In agricultural ecosystems, weeds indirectly affect crops via phytophagous insects that feed on both weeds and crops. In paddy fields, heteropteran insects are among the most serious pests of rice plants. In some heteropterans, the proboscis is used to suck rice ears, inducing black spots on the grains (i.e., pecky rice). Even a low proportion of pecky rice (>0.1%) significantly decreases the market price of rice; in Japan, this problem has led to severe economic losses. Because heteropterans feed on the reproductive organs of weeds as well as rice plants, various weeds that grow around paddy fields may increase the populations of heteropterans that cause pecky rice. To clarify which types of weeds can be used by heteropterans causing pecky rice, we investigated the interactions between plants (including rice plants) and heteropterans in an agricultural landscape in Hyogo, Japan. We observed 833 individuals of 27 heteropteran species (13 families) feeding on the reproductive organs of 35 plant species (Poales: three families) including rice plants from June to October 2019. All heteropteran species were native, whereas six of 35 plant species were non‐native. We found 12 heteropteran species on rice plants; nine of the 12 heteropteran species fed on weeds (a total of 32 species) as well as rice plants, whereas the other three species fed exclusively on rice plants. Heteropterans fed on native weeds throughout the growing seasons (June–October), but on non‐native weeds only before rice plants bloomed (June–July). Therefore, diverse weed species that grow around paddy fields are food resources for heteropteran insects and they might indirectly increase the incidence of pecky rice. [ABSTRACT FROM AUTHOR]

Nutrient enrichment of rivers and lakes has been increasing rapidly over the past few decades, primarily because of agricultural intensification. Although nutrient enrichment is known to drive excessive algal and microbial growth, which can directly and indirectly change the ecological community composition, the resulting changes in food web emergent properties are poorly understood. We used ecological network analysis (ENA) to examine the emergent properties of 12 riverine food webs across a nutrient enrichment gradient in the Manawatu, New Zealand. We also derive Keystone Sensitivity Indices to explore whether nutrients change the trophic importance of species in a way that alters the resilience of the communities to further nutrient enrichment or floods. Nutrient enrichment resulted in communities composed of energy inefficient species with high community (excluding microbes) respiration. Community respiration was several times greater in enriched communities, and this may drive hypoxic conditions even without concomitant changes in microbial respiration. Enriched communities exhibited weaker trophic cascades, which may yield greater robustness to energy flow loss. Interestingly, enriched communities were also more structurally and functionally affected by species sensitive to flow disturbance making these communities more vulnerable to floods. [ABSTRACT FROM AUTHOR]